1. Field of the Invention
The present invention relates to a three-dimensional shape measuring method and a three-dimensional shape measuring apparatus for measuring a three-dimensional shape of an electronic component, a solder bump, or a conductive paste, for example, by a light-section method.
2. Description of the Related Art
Requests have been made for carrying out 100% inspection of objects for measurement such as electronic components in a non-destructive manner and measuring a three-dimensional shape of an object in a non-contact manner in order to rapidly carry out the inspection. A light-section method is known as one of these measuring methods.
The above light-section method is a method of projecting a slit light on the object on a measurement table, taking in a beam-split image reflected by the object by a camera as image data, and obtaining a three-dimensional shape (such as a position of unevenness) on a surface of the object by the principle of triangulation. It has been used in an inspection apparatus for apparel and medical use.
In addition, in the above light-section method, a method of projecting not a single slit light but a plurality of slit lights (hereinafter, referred to as the “multi-slit light”) simultaneously on the object for measurement (a pattern light projection method) is effective. This is because measurement of a plurality of points is simultaneously performed, and the time of measurement can be considerably shortened.
In another conventional light-section method, shown in FIG. 12, a method has been employed, in which, in the measurement of a three-dimensional shape utilizing a multi-slit method, a spot light emitted from a light source 21 (for example, a laser beam source is used for a light source from the viewpoint of the characteristics of high brightness and light collection) is formed into a single slit light by a slit forming means 22 such as a cylindrical lens, and a multi-slit light 24 is formed by a scanning mechanism 23 such as a polygon mirror. The multi-slit light is projected on the object for measurement, and the reflected light is picked up by an image pickup optical system (not shown) to measure a three-dimensional shape.
When the multi-slit light is projected on the object for measurement in order to enable the measurement of the three-dimensional shape with high accuracy, it is necessary to adjust the focus on the object for measurement, and to project the multi-slit light without any blur Differences in the heights of objects for measurement, for example, may make it difficult to adjust the focus in every area of the object for measurement when projecting the multi-slit light. To solve this problem, the focal depth of the projection optical system may be increased, and the use of a diaphragm in a projection optical system for this purpose has been known as a general optical technology.
However, if a diaphragm is used in the projection optical system, there is a balance between the critical values of the focal depth and the quantity of light. In other words, the smaller the diameter of the diaphragm (an aperture), the larger the focal depth. However, there is a disadvantage that the quantity of light is reduced. If the quantity of light is too small, reliability of the result of measurement is degraded, and measurement of high accuracy cannot be performed.